The present invention relates to an imaging device, a control method for the imaging device, a program for performing the control method, and a recording medium recording the program, and is applicable to a monitoring device, for example. The imaging device according to the present invention includes a controller for comparing a focal depth detected according to a current position of a zoom lens and an imaging range where a focused image is ensured at the current position of the zoom lens and for switching between autofocus control using an evaluation value and focus control by a cam curve according to the result of this comparison, so that the reliability of a focus adjusting mechanism can be greatly improved over the related art in an imaging device using an inner focus type lens or the like.
An imaging device in related art such as a video camera has a function of autofocus control. As disclosed in Japanese Patent Laid-open No. Hei 3-220876, for example, the autofocus control is such that a high-frequency signal component is extracted from an imaging result and is integrated to thereby calculate an evaluation value indicative of the degree of focusing and that a focus lens is moved by a so-called hill-climbing method using this evaluation value to thereby form a focusing condition.
Such an imaging device employs an inner focus type lens to realize a compact size. In the inner focus type lens, the focus lens must be maintained at a proper position relative to the zoom lens according to a subject distance from the lens to a subject in performing zoom-in and zoom-out operations. Accordingly, in such an inner focus type imaging device, the focus lens is maintained at a proper position relative to the zoom lens in combination with the autofocus control, thereby allowing the imaging of a desired subject with magnification.
There is a case that this kind of imaging device is used for a monitoring device. In this case, the imaging device is used continuously for a long period of time, and zoom-in and zoom-out operations are performed by remote control as required.
If the autofocus control by a hill-climbing method is performed in such a case, a focus adjusting mechanism is operated continuously for a long period of time, causing an excessive load on the focus adjusting mechanism. As a result, the reliability of the focus adjusting mechanism is rapidly reduced.